SD, when similar questions have arisen in the past, my view has been that the back surrounds(yes, even with QSs two should be better and allow for a "stereo" back effect on some passages)should be at least 4' behind the listening position to give room for a rear sound field to form. Because of the exceptionally wide dispersion of the QSs, even 3-4' back would give a reasonable effect, but twice that distance should be better if available.
As Dan pointed out, you've given distances behind the side surrounds, which may not be the same as distances behind the listening position (those are the exact distances from the listening position as the sides are perfectly lined up with the heads of the listener in the main seating area) if the side surrounds are farther back than the listening position. Be that as it may, placing the QS8 about 9' back on the rear wall and about 3' above ear level should give a deeper back surround effect(assuming that the path is unobstructed)than would result from placing it on that 8" partition about 8' up and 3' back.
the side surrounds are exactly positioned at the sides of the main listening area which is exactly 4' away from where option 1 is and approximately 8 - 9' from option 2.
i was a little concerned about the back surround being so far away from the listening position placing it at twice the distance of the front soundstage from the main listening position.
i'd also gathered that calibration should compensate and take care of that distance. of course i wanted to hear from someone who had a setup like i described in options 1 & 2 to hear what they had to say. i could envision how good it might sound if i could place that center back channel that far away and what an incredible effect it would have on the movie experience especially 6 or 7 channel discrete movies as well as matrixed 5 channel events too. (i only matrix DD or DTS lossy, never lossless--that's just me)
so johnk, i'll gather you vote for the farther back position for the center back channel!?! thanks for your insight and recommendation. i think that the further back postioning of the center back channel will have a hugh positive effect on the audio events!